Heat exchangers used for recovery of heat from the waste water of sanitary showers in the prior art require dedicated/independent water heating units to ensure balanced flow rates of the heat mediating fluids for optimal performance. Heat recovering shower installations that share the hot water supply with other hot water facilities typically transfer the recovered heat only to the shower's cold water supply which significantly reduces or limits the operational effectiveness of the heat exchanger. Shower installations using heated water from heated water utilities that are not exclusive or dedicated (i.e. that can supply heated water simultaneously to additional separate hot water taps or outlets) with heat exchange devices (HXDs) according to the prior art are affected by unbalanced fluctuations in or disturbances to the balanced flow of heat mediating fluids through the heat exchange devices and consequently they experience reductions in the amount of useful heat that is recovered. The economical and environmental benefit of using heat exchange devices is especially significant for communal facilities having multiple shower installations that are extensively used, such as for sports clubs or public swimming pools, and these generally use centralised (multiple facility supplying) water heating units, which are more cost effective. There is a need to improve the performance of such systems having heat exchange devices so as to reduce the effects of such fluctuations and disturbances in the fluid flow and thereby improve the performance of the heat exchanger devices.